#!/usr/bin/env python3
# -*- coding:utf-8 -*-
# Author:liang futing
#@Time :2019/5/22 15:20
from decimal import Decimal
from django.conf import settings
from shop.models import Product
class Cart:
    def __init__(self,request):
        self.session=request.session
        cart=self.session.get(settings.CART_SESSION_ID)
        if not cart:
            cart=self.session[settings.CART_SESSION_ID]={}
        self.cart=cart

    def add(self,product,quantity=1,update_quantity=False):
        '''
        向购物车增加商品
        :param product:
        :param quantity:
        :param update_quantity:
        :return:
        '''
        product_id=str(product.id)
        if product_id not in self.cart:
            self.cart[product_id]={'quantity':0,'price':str(product.price)}
        if update_quantity:
            self.cart[product_id]['quantity']=quantity
        else:
            self.cart[product_id]['quntity']+=quantity
        self.save()

    def save(self):
        '''
        设置session.modfied的值 为True,中间件在看到这个属性的时候就会保存session
        :return:
        '''
        self.session.modified=True

    def remove(self,product):
        product_id=str(product.id)
        if product_id in self.cart:
            del self.cart[product_id]
            self.save()

    def __iter__(self):
        product_ids=self.cart.keys()
        products=Product.objects.filter(id__in=product_ids)
        cart=self.cart.copy()

        for product in products:
            cart[str(product.id)]['product']=product
        for item in cart.values():
            item['price']=Decimal(item('price'))
            item['total_price']=item['price']*item['quantity']
            yield item

    def __len__(self):
        '''
        显示购物车共有几种商品
        :return:
        '''
        return sum(item['quantity'] for item in self.cart.values())

    def get_total_price(self):
        return sum( Decimal(item['price']*item['quantity']) for item in self.cart.values())

    def clear(self):
        del self.session[settings.CART_SESSION_ID]
        self.save()